Question

Consider the following statements: 
(i) Sound pressure changes with distance from the source 
(ii) Sound power is a property of the source 
(iii) Sound intensity is sound power per unit volume 
Choose the correct option from the following:
 

• A. (i), (ii), and (iii) are correct
• B. only (i) and (ii) are correct
• C. only (i) and (iii) are correct
• D. only (ii) and (iii) are correct

Hint:

- Sound pressure varies with distance and is affected by the environment.
- Sound power is constant for a given source.
- Sound intensity is measured in \( {W/m}^2 \), not per unit volume.

Answer 1

The Correct Option is B

Step 1: Analyzing Statement (i).
Sound pressure refers to the local pressure deviation from the ambient atmospheric pressure caused by a sound wave. As the sound wave travels away from the source, the energy spreads out and the pressure amplitude generally decreases. So, statement (i) is correct.

Step 2: Analyzing Statement (ii).
Sound power is the total amount of energy emitted by a source per unit time and is independent of the environment. It is an intrinsic property of the source. Thus, statement (ii) is correct.

Step 3: Analyzing Statement (iii).
Sound intensity is defined as the sound power per unit area (not volume). It quantifies the power that passes through a certain area perpendicular to the direction of the wave. Therefore, statement (iii) is incorrect.

Hence, only statements (i) and (ii) are correct.